1577 Using CTS5 Calculator to Predict The 5-10-Year Risk of Late Distant Recurrence for Women With ER-Positive Breast Cancer Who Are Recurrence-Free 5 Years After Endocrine Therapy and To Reduce the Number of Patients Needing Discussion for The Extended Endocrine Therapy in The Breast MDTs: A Quality Improvement Project

Introduction The increasing number of patients has created a pressure on the services provided that aim to ensure the maximum level of care, particularly MDT meetings. Using the CTS5 calculator can readily reduce the number of patients needing discussion for EET. This is will prevent delays in decisions made for patients and more importantly, an evidence-based tool will be used for more accurate results. Method A retrospective data collection was undertaken from the Breast MDT records, initially dating from January to December 2018. Then when the optional use of CTS5 was established, data were retrieved from August to October 2019. As per guidance for the use of the CTS5 calculator; Women were deemed low risk if their 5–10-year risk is less than 5%, intermediate if between 5–10%, and high risk if their 5–10-year risk is more than 10%. Finally, a prospective data collected from January to March 2020 where an agreement was made for all involved Surgeons to use the CTS5 calculator. Results Before Introducing the CTS5 Calculator, in 2018, the number of patients was 1523 from which 66 were for EET 4.3%. When CTS5 Calculator was first introduced, 1st of August - 31st October 2019, the percentage reduced to 4.1% and from January to March 2020, a further reduction 3.9% was noticed. Conclusions The CTS5 calculator is an effective evidence-based tool used to predict the risk of 5-10 years recurrence in breast cancer patients. Implementing it will reduce the number of patients needing discussion in Breast MDTs, sparing meetings’ and patients’ time.

Breast Cancer Index and prediction of benefit from extended endocrine therapy based on treatment compliance: An IDEAL study.

531 Background: The IDEAL trial randomized hormone receptor-positive (HR+) breast cancer patients to 5 vs 2.5y of extended letrozole after completion of 5y of adjuvant endocrine therapy. In the parent trial, approximately 60% of patients overall were compliant with endocrine treatment (59% vs 74% compliance in 5y and 2.5y arms, respectively), with patient experiences as the most significant factors leading to treatment discontinuation. Breast Cancer Index is a gene expression-based signature that predicts which HR+ patients are likely to benefit from extended endocrine therapy (EET) vs those unlikely to benefit [BCI (H/I)-High and -Low, respectively]. The current study examined EET compliance and outcome by BCI (H/I) status in patients treated in the IDEAL trial. Methods: Patients with available primary tumor specimens were eligible for this blinded study. Primary endpoint was recurrence-free interval (RFI), including locoregional and distant recurrences. Kaplan-Meier and Cox proportional hazards regression analysis were used to analyze the benefit of EET. Non-compliance was defined as completion of ≤60% of treatment duration (≤3y for 5y arm; ≤1.5y for 2.5y arm) for any reason other than disease events. Overtreatment was defined as % compliant BCI (H/I)-Low patients in the 5y arm; undertreatment was % noncompliant BCI (H/I)-High patients in the 5y arm. Results: 908 HR+ patients (73% pN+, 59y, 45% pT1, 48% pT2) were included. 78% (n = 708) of patients were compliant, of which 48% (n = 338) were BCI (H/I)-High and 52% (n = 370) were BCI (H/I)-Low. In non-compliant patients (22%, n = 200), 45% (n = 91) were BCI (H/I)-High and 55% (n = 109) were BCI (H/I)-Low. BCI (H/I)-Low patients irrespective of compliance status did not derive significant benefit from EET (P = 0.922, compliant subset; 0.894 non-compliant subset). Compliant BCI (H/I)-High patients showed significant benefit from EET (HR 0.35, 95% CI 0.16-0.79; absolute benefit 11.7%; P = 0.008) whereas non-compliant BCI (H/I)-High patients did not (HR 0.75, 95% CI 0.17-3.35; absolute benefit 2.1%, P = 0.704). In this study, 38% of patients in the 5y EET arm were BCI (H/I)-Low and compliant and thus were overtreated, while 13% of patients in the 5y EET arm were BCI (H/I)-High and non-compliant and thus were undertreated. Conclusions: Patients that were BCI (H/I)-Low did not derive significant benefit from 5 vs 2.5y of EET even when compliant, and thus may be considered for treatment de-escalation. Importantly, BCI (H/I)-High patients with endocrine responsive disease showed significant improvements in outcome when compliant and should be guided to continue treatment. BCI may serve as an important genomic tool to increase EET compliance and identify patients that may be candidates for increased side effect management and support to potentially improve outcomes. Clinical trial information: NTR3077; BOOG 2006-05; Eudra-CT 2006-003958-16.

Evaluation of the ability of the Clinical Treatment Score at 5 years (CTS5) compared to other risk stratification methods to predict the response to an extended endocrine therapy in breast cancer patients

Purpose Extension of adjuvant endocrine therapy (ET) reduces the risk of recurrence in women diagnosed with ER-positive breast cancers, but a significant benefit is unlikely to happen to all individual patients. This study is aimed at evaluating the ability of different clinical late distant recurrence (LDR) risk stratification methods and in particular the clinical treatment score at 5 years (CTS5) to predict the response to extended adjuvant ET. Methods 783 patients diagnosed with ER+ BC between 1988 and 2014 at Umberto I Hospital of Turin, of which 180 received an extended adjuvant ET, were retrospectively selected. They were stratified according to pT, pN, disease stage, tumor grade, Ki67 level, progesterone receptor status and CTS5. The primary endpoint was LDR rate. LDR rates according to ET duration were confronted in each subgroup. Result The median duration of extended ET was 7 years (6–10). Median follow-up from diagnosis was 9 years (6–26). Retrospective risk stratification according to tumor size, nodal status, disease stage, tumor grade, Ki67 level, and progesterone receptor status did not appear to be able to predict the response to extended ET. In the CTS5 high-risk subgroup instead, the risk of developing an LDR was significantly lower in the patients who underwent extended ET compared to standard ET (HR 0.37, 95% CI 0.15–0.91), while no significant benefit was demonstrated for low and intermediate-risk patients. Conclusions Risk stratification according to CTS5 appeared to be predictive of the response to extended endocrine therapy in our population of real-life pre and postmenopausal patients.

The clinical utility of gene expression assays in breast cancer patients with 0–3 involved lymph nodes

Multigene expression assays are prognostic for recurrence in hormone-receptor positive 2 (HER-2) negative breast cancer, and, in some cases, predictive of benefit from chemotherapy or extended endocrine therapy. The results of these assays may be used to guide treatment recommendations for early HER-2 negative breast cancer. We review the results of trials establishing the clinical utility of several commercially available gene expression assays.

Clinical validity of clinical treatment score 5 (CTS5) for estimating risk of late recurrence in unselected, non-trial patients with early oestrogen receptor-positive breast cancer

Purpose Clinical Treatment Score at 5 years (CTS5) is a prognostic tool to estimate distant recurrence (DR) risk after 5 years of endocrine therapy for postmenopausal women with oestrogen receptor-positive (ER-positive) breast cancer. Methods The validity of CTS5 was tested in a retrospective cohort of patients diagnosed with early ER-positive breast cancer. The primary endpoint was DR in years 5–10. The primary analysis cohort consisted of postmenopausal women, with premenopausal women as a secondary analysis cohort. Cox regression models were used to determine the prognostic value of CTS5 and Kaplan–Meier curves were used with associated 10-year DR risks (%). Results 2428 women were included with a median follow-up of 13.4 years. The CTS5 was significantly prognostic in both postmenopausal (N = 1662, HR = 2.18 95% CI (1.78–2.67)) and premenopausal women (N = 766, HR = 1.84 95% CI (1.32–2.56)). The 10-year DR risks were 2.9% (1.9–4.5), 7.2% (5.3–9.9), and 12.9% (10.0–16.7) for low, intermediate and high risk in postmenopausal women and 3.8% (2.2–6.7), 6.9% (4.4–10.8), and 11.1% (7.4–16.5) in premenopausal women, respectively. The number of observed DRs was significantly greater than expected in those predicted to be at high risk by CTS5 but this discordance was lost when those receiving more than 60 months of endocrine therapy were excluded. Conclusions The CTS5 demonstrated clinical validity for predicting late DR within a large cohort of unselected postmenopausal patients but less so in premenopausal patients. Calibration of the CTS5 was good in patients who did not receive extended endocrine therapy. The CTS5 low-risk cohort has risk of DR so low as to not warrant extended endocrine therapy.

Breast cancer index (BCI) predicts benefit of two-and-a-half versus five years of extended endocrine therapy in HR+ breast cancer patients treated in the ideal trial.

512 Background: For postmenopausal women with hormone receptor positive (HR+) breast cancer, the optimal duration of extended endocrine therapy (EET), after completing 5 years of initial aromatase inhibitor (AI)–based adjuvant therapy, remains unclear. BCI [HOXB13/IL17BR (H/I)] is a gene expression-based biomarker that has been demonstrated to predict EET benefit in the MA.17 and Trans-aTTom studies in patients treated with adjuvant tamoxifen. The current study examined the ability of BCI (H/I) to predict endocrine benefit from 2.5 vs. 5 years of extended letrozole in the IDEAL trial. Methods: All patients with available tumor specimens were eligible for this blinded prospective-retrospective study. The primary endpoint was Recurrence-Free Interval (RFI). Median follow-up was 9.1 years from randomization. Kaplan-Meier and Cox proportional hazards regression analysis were used to analyze the differential benefit of EET with statistical significance of the interaction between BCI (H/I) and treatment assessed by likelihood ratio test. Results: 908 HR+ patients (73% pN+, median 59y, 45% pT1, 48% pT2, disease free at 2.5 years) were included, with 88% and 68% receiving prior treatment with an AI or chemotherapy, respectively. BCI by H/I status (High vs. Low) was significantly predictive of response from extended letrozole in the overall (N = 908) and pN+ (N = 664) cohorts. Notably, BCI (H/I) predicted EET benefit in patients that received any primary adjuvant therapy with an AI (N = 794). Treatment to biomarker interaction was significant in the overall (p = 0.045), pN+ (p = 0.029) and any prior AI (p = 0.025) cohorts, adjusted for age, pT stage, grade, nodal status, prior endocrine therapy and prior chemotherapy. Conclusions: Novel findings from this study demonstrate that BCI predicts endocrine benefit from extended letrozole in postmenopausal patients treated with primary adjuvant AI. These results support the growing body of evidence that BCI by H/I status predicts preferential endocrine response in distinct subgroups of patients, and further support its role as an important genomic tool to inform the risk-benefit regarding duration of extended endocrine therapy. Clinical trial information: NTR3077, BOOG 2006-05, Eudra-CT 2006-003958-16 . [Table: see text]

HER2 status and prediction of extended endocrine benefit with breast cancer index (BCI) in HR+ patients in the adjuvant tamoxifen: To offer more? (aTTom) trial.

522 Background: BCI is a validated gene expression-based assay that stratifies patients based on risk of overall (0-10y) and late (post-5y) distant recurrence (DR) and predicts likelihood of benefit from extended endocrine therapy (EET). The Trans-aTTom study established Level1B validation for BCI (H/I) to predict benefit from EET.1 In this updated Trans-aTTom analysis including HER2 status, BCI (H/I) and prediction of endocrine benefit were further characterized. Methods: Centralized HER2 was determined for all cases according to current ASCO/CAP guidelines. Kaplan-Meier and Cox proportional hazards regression were conducted to assess primary and secondary endpoints of Recurrence-Free Interval (RFI) and Disease-Free Interval (DFI), respectively. A three-way interaction using likelihood ratio testing, which included treatment, BCI (H/I) and HER2, was performed to assess the effect of HER2 on BCI (H/I) prediction of EET benefit. Results: Of 789 N+ patients, 90% (N = 711) and 9% (N = 72) were HR+/HER2- and HR+/HER2+, respectively. In the HER2- subset, BCI (H/I)-High (48%) showed significant benefit from 10y vs. 5y of tamoxifen (9.4% RFI: HR = 0.35 [95% CI 0.15-0.81]; P = 0.047) while BCI (H/I)-Low patients did not (-2.1% RFI; HR = 1.15 [95% CI 0.78-1.69]; P = 0.491). For DFI, BCI (H/I)-High patients also showed significant benefit (10.3% DFI; HR = 0.41 [95% CI 0.18-0.91]; P = 0.047) while BCI (H/I)-Low patients did not (-1.7% DFI; HR = 1.10 [95% CI 0.75-1.62] P = 0.612). As demonstrated in the overall N+ cohort, significant interaction between BCI (H/I) and treatment was shown in the HER2- subset (RFI P = 0.045; DFI P = 0.044). Notably, three-way interaction evaluating BCI (H/I), treatment and HER2 status was not statistically significant (P = 0.85), indicating the ability of BCI (H/I) to predict benefit of EET activity was not significantly affected by HER2 status. Conclusions: In this updated Trans-aTTom analysis with HER2 data, BCI (H/I) showed similar predictive performance for EET response in the HER2- subset when compared to the overall N+ cohort. These data further support the clinical utility of BCI (H/I) as a predictive biomarker for informing EET benefit in HR+/HER2- and HR+/HER2+ disease. Clinical trial information: NCT00003678 . [Table: see text]